Crawly

Overview

Crawly is an application framework for crawling web sites and extracting structured data which can be used for a wide range of useful applications, like data mining, information processing or historical archival.

Requirements

1. Elixir "~> 1.10"
2. Works on Linux, Windows, OS X and BSD

Quickstart

1. Add Crawly as a dependencies:

   # mix.exs
   defp deps do
       [
         {:crawly, "~> 0.13.0"},
         {:floki, "~> 0.26.0"}
       ]
   end
   

2. Fetch dependencies: $ mix deps.get

3. Create a spider

   # lib/crawly_example/esl_spider.ex
   defmodule EslSpider do
     use Crawly.Spider
     
     alias Crawly.Utils
   
     @impl Crawly.Spider
     def base_url(), do: "https://www.erlang-solutions.com"
   
     @impl Crawly.Spider
     def init(), do: [start_urls: ["https://www.erlang-solutions.com/blog/"]]
   
     @impl Crawly.Spider
     def parse_item(response) do
       {:ok, document} = Floki.parse_document(response.body)
       hrefs = document |> Floki.find("a.btn-link") |> Floki.attribute("href")
   
       requests =
         Utils.build_absolute_urls(hrefs, base_url())
         |> Utils.requests_from_urls()
   
       title = document |> Floki.find("h1.page-title-sm") |> Floki.text()
   
       %{
         :requests => requests,
         :items => [%{title: title, url: response.request_url}]
       }
     end
   end
   

4. Configure Crawly

   • By default, Crawly does not require any configuration. But obviously you will need a configuration for fine tuning the crawls:

   # in config.exs
   config :crawly,
     closespider_timeout: 10,
     concurrent_requests_per_domain: 8,
     middlewares: [
       Crawly.Middlewares.DomainFilter,
       Crawly.Middlewares.UniqueRequest,
       {Crawly.Middlewares.UserAgent, user_agents: ["Crawly Bot"]}
     ],
     pipelines: [
       {Crawly.Pipelines.Validate, fields: [:url, :title]},
       {Crawly.Pipelines.DuplicatesFilter, item_id: :title},
       Crawly.Pipelines.JSONEncoder,
       {Crawly.Pipelines.WriteToFile, extension: "jl", folder: "/tmp"}
     ]
   

5. Start the Crawl:

   • $ iex -S mix
   • iex(1)> Crawly.Engine.start_spider(EslSpider)

6. Results can be seen with: $ cat /tmp/EslSpider.jl

Need more help?

I have decided to create a public telegram channel, so it's now possible to be connected, and it's possible to ask questions and get answers faster!

Please join me on: https://t.me/crawlyelixir

Browser rendering

Crawly can be configured in the way that all fetched pages will be browser rendered, which can be very useful if you need to extract data from pages which has lots of asynchronous elements (for example parts loaded by AJAX).

You can read more here:

• Browser Rendering

Experimental UI

The CrawlyUI project is an add-on that aims to provide an interface for managing and rapidly developing spiders.

Checkout the code from GitHub or try it online CrawlyUIDemo

See more at Experimental UI

Documentation

• API Reference
• Quickstart
• Tutorial

Roadmap

1. [x] Pluggable HTTP client
2. [x] Retries support
3. [x] Cookies support
4. [x] XPath support - can be actually done with meeseeks
5. [ ] Project generators (spiders)
6. [ ] UI for jobs management

Articles

1. Blog post on Erlang Solutions website: https://www.erlang-solutions.com/blog/web-scraping-with-elixir.html
2. Blog post about using Crawly inside a machine learning project with Tensorflow (Tensorflex): https://www.erlang-solutions.com/blog/how-to-build-a-machine-learning-project-in-elixir.html
3. Web scraping with Crawly and Elixir. Browser rendering: https://medium.com/@oltarasenko/web-scraping-with-elixir-and-crawly-browser-rendering-afcaacf954e8
4. Web scraping with Elixir and Crawly. Extracting data behind authentication: https://oltarasenko.medium.com/web-scraping-with-elixir-and-crawly-extracting-data-behind-authentication-a52584e9cf13
5. What is web scraping, and why you might want to use it?
6. Using Elixir and Crawly for price monitoring

Example projects

1. Blog crawler: https://github.com/oltarasenko/crawly-spider-example
2. E-commerce websites: https://github.com/oltarasenko/products-advisor
3. Car shops: https://github.com/oltarasenko/crawly-cars
4. JavaScript based website (Splash example): https://github.com/oltarasenko/autosites

Contributors

We would gladly accept your contributions!

Documentation

Please find documentation on the HexDocs

Production usages

Using Crawly on production? Please let us know about your case!